标签FacetGrid

Question

我有这样的数据。

big_category category variable value
a aa111111111 x 1.2
a ba111111111 x 1.05
a ca111111111 x 1.11
a aa111111111 y 1.43
a ba111111111 y 1.09
a ca111111111 y 0.97
a aa111111111 z 1.12
a ba111111111 z 1.46
a ca111111111 z 1.32
b ab111111111 x 1.2
b ab111111111 y 1.05
b ab111111111 z 1.11
c ac111111111 x 1.2
c bc111111111 x 1.05
c cc111111111 x 1.11
c ac111111111 y 1.43
c bc111111111 y 1.09
c cc111111111 y 0.97
c ac111111111 z 1.12
c bc111111111 z 1.46
c cc111111111 z 1.32

代码：

big_theme <- theme(
panel.background = element_rect(fill = "black"),
plot.background = element_rect(fill = "black", colour = NA),
plot.title = element_text(hjust = 0.5, size = 15, color = "white"),
axis.text.y = element_text(colour = "white", size = 14),
axis.title.x = element_text(colour = "white", size = 14),
axis.title.y = element_text(colour = "white", size = 14),
axis.text.x = element_text(vjust = 1, angle = 45, color = "white", size = 14, hjust=1),
strip.background = element_rect(fill = "black"),
strip.text = element_text(colour = 'white'),
strip.text.y = element_text(angle = 0),
legend.position = "top"
)

theme2 = theme(panel.background = element_rect(fill = 'black'),
legend.background=element_rect(fill = "black"),
legend.text = element_text(colour = "white", size = 14),
legend.justification = "right",
legend.key.height = unit(1, "line"),
legend.key = element_rect(color = "black", fill = "black"))

theme3 = theme(plot.background = element_rect(fill = 'black'))

ggplot(sample_data %>% mutate(variable=fct_relevel(variable, c("z","x","y")))) +
geom_col(position = "identity",
aes(x = category, y = value, fill = variable, color = variable)) +
facet_grid(. ~ big_category, space="free_x", scales="free_x", switch="x") +
big_theme + theme2 + theme3 +
theme(strip.placement = "outside",
strip.background = element_rect(fill=NA,colour="white"),
panel.spacing.x=unit(0,"cm"),
strip.text = element_text(hjust=0, face="bold", size=12))

图形

我希望x轴按类别标记，下面我想要big_category的标签。我已经这样做了，但有些事我无法改变。我希望大类别标签一直到标签的左下角。现在它位于图表的左侧，但不是标签。此外，我希望能够删除少于2个类别的big_categories的big_category标签。